copyright © 2010 pearson education, inc. general characteristics of viruses differentiate a virus...
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Copyright © 2010 Pearson Education, Inc.
General Characteristics of Viruses Differentiate a virus from a bacterium.
Obligatory intracellular parasites Contain DNA or RNA simultaneously in the virion Contain a protein coat (capsid) Some are enclosed by an envelope Some viruses have spikes Most viruses infect only specific types of cells
in one host Host range is determined by specific host
attachment sites and cellular factors
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Virion Structure
Figure 13.2a
Nucleic acid DNA or RNA
Capsid Capsomeres
Envelope Spikes
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Morphology of an Enveloped Virus 3
Copyright © 2010 Pearson Education, Inc. Figure 13.16b
Enveloped Viruses 4
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Morphology of a Helical Virus 5
Copyright © 2010 Pearson Education, Inc. Figure 13.5
Morphology of a Complex Virus 6
Copyright © 2010 Pearson Education, Inc. Figure 13.6
Growing Viruses
Viruses must be grown in living cells Bacteriophages
form plaques on a lawn of bacteria
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Growing Viruses
Animal viruses may be grown in living animals or in embryonated eggs
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Virus Identification
Cytopathic effects: Detectable changes in the host cell due to viral infection (p. 441)
Blood serum (serology) tests Detect antibodies against viruses in a patient Use antibodies to identify viruses in neutralization tests,
viral hemagglutination, and Western blot
Nucleic acids: Studies of the DNA/RNA
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Copyright © 2010 Pearson Education, Inc. Figure 13.9
Virus Identification: Cytopathic Effect 10
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Lytic Cycle of a T-Even Bacteriophage
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Figure 13.11
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Figure 13.11
Lytic Cycle of a T-Even Bacteriophage 12
Copyright © 2010 Pearson Education, Inc. Figure 13.12
The Lysogenic Cycle 13
Copyright © 2010 Pearson Education, Inc. Figure 13.14a
Attachment, Entry, Uncoating
By pinocytosis
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Attachment, Entry, Uncoating
By fusion
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Copyright © 2010 Pearson Education, Inc. Figure 13.15
Multiplication of DNA Virus 16
Copyright © 2010 Pearson Education, Inc. Figure 13.17a
Sense Strand (+ Strand) RNA Virus 17
Copyright © 2010 Pearson Education, Inc. Figure 13.17b
Antisense Strand (– Strand) RNA Virus 18
Copyright © 2010 Pearson Education, Inc. Figure 13.17c
Double-Stranded RNA Virus 19
Copyright © 2010 Pearson Education, Inc. Figure 13.19
Multiplication of a Retrovirus 20
Copyright © 2010 Pearson Education, Inc. Figure 13.20
Release of an enveloped virus through ‘budding’
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